Text of the card does not specify any duration of the effect of its discarding. I think that it is a mistake.A Panoply of Wings wrote:Playable at any tapped or untapped non-Haven, non-Shadow-hold, non-Dark-hold site in a Wilderness if the influence check is greater than 11. Standard Modifications: if Radagast is your Wizard (+3). Discard this faction to make information playable at such a site. 'Tell them to bring news of anything that bears on this matter...'-LotRII
I propose the following erratum.
"Playable at any tapped or untapped non-Haven, non-Shadow-hold, non-Dark-hold site in a Wilderness if the influence check is greater than 11. Standard Modifications: if Radagast is your Wizard (+3). Discard this faction to make information playable at such a site until end of turn. 'Tell them to bring news of anything that bears on this matter...'-LotRII"